Multi-modulation scheme compatible radio

Abstract

A transceiver compatible with both wide channel constant envelope 4 level FSK FM modulation and narrow channel π/4 differential QPSK linear modulation allows compatible interaction between modified constant envelope and non-constant envelope transmitters. All Nyquist filtering occurs in the transmitters, and none in the receiver.

What is claimed is: 
     
       1. A radio transceiver capable of transmitting and receiving quantized digital information signals having two or more levels and a predetermined symbol rate, the transceiver comprising: A) a transmitter including a filter that satisfies Nyquist's criterion for minimizing intersymbol interference, the filter having a bandwidth in Hertz of approximately one half the symbol rate; and   B) a receiver including means for amplifying a received signal and means for recovering digital information signals from the received signal; wherein, instead of distributing filtering intended to minimize intersymbol interference between the transmitter and the receiver, all such filtering occurs at the transmitter.   
     
     
       2. A radio transceiver capable of transmitting and receiving quantized digital information signals having two or more levels and a predetermined symbol rate, the transceiver comprising: A) a transmitter, comprising at least a filter that satisfies Nyquist's criterion for minimizing intersymbol interference, the filter having a bandwidth in Hertz of approximately one half the symbol rate, and means for modulating a carrier frequency with a digital information signal, and transmitting at least one of: i) a constant envelope signal; and   ii) a non-constant envelope signal; and     B) a receiver including means for amplifying a received signal and means for recovering digital information signals from the received signal, wherein the receiver is capable of receiving and properly demodulating both: i) a constant envelope signal; and   ii) a non-constant envelope signal; wherein, instead of distributing filtering intended to minimize intersymbol interference between the transmitter and the receiver, all such filtering occurs at the transmitter.       
     
     
       3. A radio transceiver capable of transmitting and receiving quantized digital information signals having two or more levels and a predetermined symbol rate, the transceiver comprising: A) a transmitter, comprising at least a filter that satisfies Nyquist's criterion for minimizing intersymbol interference, the filter having a bandwidth in Hertz of approximately one half the symbol rate, and means for modulating a carrier frequency with a digital information signal, and transmitting at least one of: i) a constant envelope signal occupying a first spectral bandwidth; and   ii) a non-constant envelope signal occupying a second spectral bandwidth, which second spectral bandwidth is different from the first spectral bandwidth; and     B) a receiver including means for amplifying a received signal and means for recovering digital information signals from the received signal, wherein the receiver is capable of receiving and properly demodulating both: i) a constant envelope signal occupying the first spectral bandwidth; and   ii) a non-constant envelope signal occupying the second spectral band width; wherein, instead of distributing filtering intended to minimize intersymbol interference between the transmitter and the receiver, all such filtering occurs at the transmitter.       
     
     
       4. A radio transceiver capable of transmitting and receiving quantized digital information signals having two or more levels and a predetermined symbol rate, the transceiver comprising: A) a transmitter, comprising: i) a filter that satisfies Nyquist's criterion for minimizing intersymbol interference, the filter having a bandwidth in Hertz of approximately one half the symbol rate;   ii) differential encoder means coupled to the filter for filtering an input information signal to cause selective rotation of a phase value of a modulated signal by a predetermined amount; and   iii) frequency modulator means operably coupled to the differential encoder means for outputting the modulated signal; and     B) a receiver including means for amplifying a received signal and means for recovering digital information signals from the received signal, wherein the receiver is capable of receiving and properly demodulating both: i) a constant envelope signal occupying a first spectral bandwidth; and   ii) a non-constant envelope signal occupying a second spectral bandwidth, wherein the first spectral bandwidth is different from the second spectral bandwidth; wherein, instead of distributing filtering intended to minimize intersymbol interference between the transmitter and the receiver, all such filtering occurs at the transmitter.     
     
     
       5. A radio communication system, comprising: A) a first plurality of transceivers capable of transmitting and receiving quantized digital information signals having two or more levels and a predetermined symbol rate, each transceiver comprising: i) a transmitter, comprising at least a filter that satisfies Nyquist's criterion for minimizing intersymbol interference, the filter having a bandwidth in Hertz of approximately one half the symbol rate, and means for modulating a carrier frequency with a digital information signal, and transmitting a constant envelope signal occupying a first spectral bandwidth;   ii) receiver means including means for amplifying a received signal and means for recovering digital information signals from the received signal, wherein the receiver is capable of receiving and properly demodulating both: a) a constant envelope signal occupying the first spectral bandwidth; and   b) a non-constant envelope signal occupying a second spectral bandwidth, which second spectral bandwidth is different than the first spectral bandwidth; wherein, instead of distributing filtering intended to minimize intersymbol interference between the transmitter and the receiver, all such filtering occurs at the transmitter; and         B) a second plurality of transceivers capable of transmitting and receiving quantized digital information signals having two or more levels and a predetermined symbol rate, each transceiver comprising: i) a transmitter, comprising at least a filter that satisfies Nyquist's criterion for minimizing intersymbol interference, the filter having a bandwidth in Hertz of approximately one half the symbol rate, and means for modulating a carrier frequency with a digital information signal, and transmitting a non-constant envelope signal occupying the second spectral bandwidth; and   ii) receiver means including means for amplifying a received signal and means for recovering digital information signals from the received signal, wherein the receiver is capable of receiving and properly demodulating both: a) a constant envelope signal occupying the first spectral bandwidth; and   b) a non-constant envelope signal occupying the second spectral bandwidth; wherein, instead of distributing filtering intended to minimize intersymbol interference between the transmitter and the receiver, all such filtering occurs at the transmitter; such that transceivers from the first plurality of transceivers can compatibly communicate with transceivers from the second plurality of transceivers.